1. Field of the Invention
The present invention relates to a structure of an ink-jet head for forming an image by ejecting minute ink droplets onto a printing surface.
2. Description of Related Art
Conventionally, as a recording apparatus which has a simple structure and enables high speed and high quality printing, an ink-jet system recording apparatus is well known.
As a ink-jet head of the ink-jet system recording apparatus, for example, an ink-jet head of a flat plate lamination structure is known which includes a plurality of nozzles for ejecting ink onto a recording medium such as a paper, a plurality of pressure chambers provided correspondingly to the respective nozzles and connected to the nozzles, a common ink chamber for distributing and supplying ink to the pressure chambers through connection passages, and a supply passage for supplying the ink to the common ink chamber.
In this structure, the ink supplied to the common ink chamber passes through the respective connection passages and is distributed to the respective pressure chambers. When ejection energy is given in the respective pressure chambers by a suitable actuator, the ink is ejected from the corresponding nozzles.
Here, for example, at the time of exchange of an ink cartridge, when air bubbles are mixed into the ink, or air having entered from the ink cartridge or the wall surface of a supply passage grows into air bubbles, and the air bubbles enter the pressure chambers or the nozzles, non-ejection of the ink is caused. Thus, a technique is known in which a purge mechanism for removing air bubbles by forcibly sucking ink in the inside of the ink-jet head from a nozzle side by a pump or the like is provided in the ink-jet recording apparatus.
The ink supplied from the ink cartridge goes via the supply passage to flow through the inside of the common ink chamber, passes through the respective connection passages, and is distributed to the pressure chambers. At this time, air bubbles are carried on the flow of the ink and are apt to collect at the end of the common ink chamber at the most downstream side. Besides, the end of the common ink chamber at the most downstream side is a place where stagnation of the ink is apt to occur, and the air bubbles generated in the ink are apt to collect, and gradually grow to be apt to impede the flow of the ink. Accordingly, as a nozzle becomes close to the end, a trouble (missing dot) of non-ejection of ink is apt to occur.
As described above, since the ink stagnates at the end of the common ink chamber at the most downstream side, the removal of the air bubbles has been difficult even by the foregoing purge mechanism. Accordingly, there has been a problem that it becomes necessary to frequently repeat the purge operation by the purge mechanism, a large amount of ink is wastefully consumed, and the running cost rises.